First introduced by Microsoft in 2001 as a successor to Windows 2000, there were more than 400 million copies in use before Microsoft introduced Windows Vista in 2006. Despite Microsoft's decision to cease selling the operating system to OEMs and retailers in 2008 (and through its System Builders program in 2009), Windows XP remained the most widely used operating system until August 2012, when it was eclipsed by Windows 7, according to market share statistics tracker Net Applications. And while Windows 7 has taken the dominant spot with 46.64 percent market share, even at this late date Windows XP remains in second place with 31.22 percent market share, according to Net Applications.

The enterprise, in particular, has had a strong attachment to Windows XP.

"We're looking at a fairly large number of devices that are under management with us," says Chuck Brown, director of product management at Fiberlink Communications, provider cloud-based enterprise mobility management and laptop management. "What we're seeing is approximately 45 percent of the devices out there today are still on Windows XP SP3."

David Brisbois, senior manager of Assessment and Technology Deployment Services Consulting at solutions and services provider Softchoice, says his firm sees similar numbers.

"It's kind of staggering how much Windows XP is still in the environment," he says. "Half the PCs we've looked at are still on Windows XP."

Brisbois says the numbers have been going down as the April 8, 2014 deadline approaches, but it's been much slower than expected. While a number of clients have adopted a slow migration process -- they've chosen to go with Windows 7 and but are only deploying it as old hardware gets replaced--many have yet to make a choice. Even among companies that have adopted the slow migration approach, the Windows XP footprint remains large.

"Last year, 56 percent of the companies that we looked at had XP as the majority operating system," Brisbois says. "Today, 35 percent of those companies still have Windows XP as the majority. There're still stragglers in every organization."

For CIOs and other IT decision makers, the window for planning a migration to another operating system ahead of the April 14, 2014 deadline is rapidly closing, if it hasn't closed already. Windows XP machines won't stop working just because Microsoft has ceased support, of course, but Microsoft will no longer field support calls for gear running Windows XP. Microsoft will also cease providing security updates.

Start By Making an Assessment of Installed Hardware and Software

To get your arms around what you're facing, Brown says start by assessing the hardware and software installed within your enterprise.

"You need actionable intelligence on the hardware," he says. "Is it ready to support Windows 7 or Windows 8.1? You also need to assess what you have for third-party software. You have to really identify what's out there and how you're going to move it. Also, what about your enterprise licensing agreements? Is that going to cost the organization? Are you going to have to move to a different version entirely?"

Distributed organizations will have a more challenging time, Brown says, noting that they also need to anticipate the logistics of a migration.

It's Time for CIOs to Make Some Decisions

CIOs should use this situation as an opportunity to make a few key decisions about issues affecting the enterprise:

SaaS applications. Do you still need to run your productivity apps on-premises, or is SaaS a useful option? Office 365 from Microsoft, Google apps and a host of other offerings can potentially fulfill your basic app needs without requiring the care and feeding of on-prem hardware and software.

Bring your own device (BYOD). "This is a great opportunity to go down the road of at least evaluating bring your own device or choose your own device," Brisbois says. This can be an especially appealing option if your organization relies on software-as-a-service (SaaS) productivity applications, he notes. Depending on the structure of your organization, Android and iOS tablets, Mac computers, even Chromebooks may be options.

"You bring your device, regardless of platform, regardless of OS and we'll support you," says Brown, speaking of Fiberlink's MaaS360 service. "We're making sure that we support everything that's currently available with a similar united workflow for administrators. You're going to get all the same information as an administrator, regardless of platform."

Legacy Windows XP. It's likely that some machines in your organization will not be upgraded from Windows XP for whatever reason. Brisbois says you should seek to identify those machines now and come up with a plan for maintaining them.